Fix the branch name that Travis uses

Author: Seulgi Kim

.travis/check-change

@@ -84,7 +84,7 @@ push)
  # we can find common ancestor of master and the branch.
  echo "Branch push"
  git fetch origin master:master;
- COMMIT_RANGE="origin/master..${TRAVIS_COMMIT}"
+ COMMIT_RANGE="master..${TRAVIS_COMMIT}"
  fi
  ;;
 pull_request)